The thorax is a bony cage formed by the ribs and sternum. This cage articulates with and is supported by the vertebral column. It houses and protects the major organs of the cardiovascular and respiratory systems and provides the mechanism for respiration. The thoracic cage also acts as the foundation for bones and muscles of the upper extremity.

The spaces between the ribs and sternum of the bony cage are comprised primarily of skeletal muscles. These muscles maintain the integrity of the thorax and assist during respiration.